The present invention relates to an apparatus for and a method of generating electricity and, in particular, to an apparatus for and a method of using fluid flow to generate electrical energy.
Wind energy is normally converted into electrical energy by converting the energy in wind flow to the rotary motion of a mechanical device such as a windmill. The rotary motion is applied to an electrical generator to produce electrical power. The change from wind power to electrical energy involves intermediate mechanical stages, including feathering and gearing systems, that increase the cost and complexity of the device. Consequently, windmills are cost effective only in isolated areas or on wind farms in high wind regions. Therefore, the known windmills are seldom used on single family dwellings or small buildings.
In a similar manner, hydroelectric power uses the pressure of falling water to rotate a turbine that produces electrical energy. However, the mechanical transducers used require an appropriate dam site for extensive power generation. Therefore, hydroelectric power is also not appropriate or cost effective for single family dwellings.
In order to eliminate many of the limitations associated with the mechanical linkages used in traditional windmills and hydroelectric plants, devices for the direct conversion of wind power to electrical power have been proposed. In one such device, wind power is utilized to move charged droplets entrained in the wind from a charging electrode to electrical ground. In another device, charged particles entrained in a wind are moved by the wind against an electrostatic potential. However, both of the previously known devices require complicated systems to continually produce the charged species. Further, large wind cross sections are necessary to utilize the energy in the low density gas.
In light of the foregoing, an apparatus and method for efficiently generating electrical energy from fluid flow would be highly beneficial. The apparatus and method should allow for the conversion of fluid flow to electrical energy while minimizing, or eliminating, the mechanical linkages that increase the cost and decrease the reliability of the known devices. Additionally, the apparatus and method should produce maximal transduction per unit wind cross sectional area in order to limit the overall size of the apparatus for effective use on smaller buildings. Further, the apparatus and method should be able to utilize either a compressible fluid (i.e., air) or an incompressible fluid (i.e., water). In addition, the apparatus should be closed so that any charge moved in order to generate the electrical energy remains in the apparatus for reuse. Preferably, the apparatus is also lightweight, economical, and environmentally friendly.
The problems associated with the known devices are overcome to a large extent by an apparatus in accordance with the present invention. The present invention uses the motion of charged particles or counterions relative to a fixed surface charge of opposite polarity to produce an electrical streaming potential and current. The counterion motion occurs in pores having the fixed surface charge, which are generally perpendicular to the motion of a fluid. The. counterions are caused to move into the pores by a pressure differential which is produced within the pores by the flow of the fluid over the pores.
In one of its aspects, the present invention comprises an apparatus for generating electrical energy. The apparatus comprises a generator and a convertor operatively connected to the generator via a first and a second electrode.
The generator comprises a conducting layer and an insulating layer for electrically isolating an electrolytic solution from the conducting layer. In one embodiment, the conducting layer and the insulating layer are formed as a generally planar sheet. Alternatively, the conducting layer and the insulating layer may be formed as a capillary tube or elongate tubular member. The generator may further comprise a receptacle for storing the electrolytic solution.
A plurality of pores or channels extend through both the conducting and the insulating layers. The pores form exposed sections of the conducting layer and the insulating layer within the pores. The exposed sections of the insulating layer are charged.
In one embodiment, the insulating layer is composed of a material having a surface charge and the charge is accordingly produced directly by the insulating layer. For example, the insulating layer can be composed of glass (silicon dioxide) that has acquired a net negative surface charge by treating the glass with base. Alternatively, the exposed sections of the conducting and insulating layers may be charged by, for example, coating those sections with a charged material. The technology of such charged surface coatings is extensively developed for coating glass or quartz capillaries in capillary electrophoresis. See, e.g., Altria, xe2x80x9cCapillary Electrophoresis Guidebookxe2x80x9d or Li, xe2x80x9cCapillary Electrophoresisxe2x80x9d.
The convertor, along with the first and second electrodes, are connected to the generator for converting a current flowing through the conducting layer and the electrolytic solution into electrical energy. The first electrode is operatively connected with the conducting layer, while the second electrode is disposed to contact the electrolytic solution. Accordingly, the convertor is connected between the first and the second electrodes for converting the current flowing through the conducting layer and the electrolytic solution into electrical energy.
In another of its aspects, the present invention relates to a method for generating electrical energy. The method comprises the step of utilizing an insulating layer to electrically isolate an electrolytic solution comprising charged species from a conducting layer. A plurality of pores extend through both the conducting and the insulating layers.
Regions of the insulating layer, or regions of both the insulating and conducting layer, within the pores are formed with a charge having a polarity opposite to counterions of the electrolytic solution.
A fluid is then flowed over the conducting layer. The flow of the fluid creates a pressure differential within the pores which causes the charged species of the electrolytic solution to pass into the pores. The movement of the charged species past the charge on the exposed sections of the insulating and/or conducting layers creates a streaming potential and current which are converted into electrical energy.